[Sidefx-houdini-list] export 2d track to 3d

Louis Dunlevy ld at dneg.com
Mon Mar 17 13:15:02 EDT 2008


The short hacky answer is just parent it to the camera, make it the same 
aspect ratio as your plate and move it down z 'till it looks right! 
Works 99% of the time ;)

I always use the same camera frustrum asset so I don't have to think 
about it too much.. all those numbers..

jose fernandez wrote:
> How can I automatically fit a grid to camera, regardless of it's 
> distance on Z (what expression could I use)?
> Louis Dunlevy wrote:
>   
>> If you have the channels normalized in CHOPs all you need to do is fit a 
>> grid to the camera and creep a point driven by chops onto it. There are 
>> lots of ways to approach it but it kinda boils down to that type of thing..
>>
>> jose fernandez wrote:
>>   
>>     
>>> Well basically have a point in an arbitrary place in 3d space, that 
>>> moves proportionally in screen space as the 2d track. no matter where 
>>> the camera is...
>>>
>>> brian goodwin wrote:
>>>   
>>>     
>>>       
>>>> There many solutions to this,
>>>> but to get a better idea of what u are trying to achieve,
>>>>
>>>> are you trying to use the 2D track in 3 Dimentions or just have a flat plane
>>>> with locators that move on that flat place?
>>>>
>>>>
>>>>
>>>> On Mon, Mar 17, 2008 at 3:09 PM, jose fernandez <
>>>> jose.fernandez at framestore-cfc.com> wrote:
>>>>
>>>>   
>>>>     
>>>>       
>>>>         
>>>>> Hi I'm trying to export a 2d track into 3d space. I've brought in the
>>>>> data through chops and fitted it to uv space (0-1) through a range node
>>>>> (1-2048 in x, 1-1556 in y).
>>>>> My first try was to use a grid at a certain point to project uv
>>>>> cordinates from camera... and transferring attributes between chops and
>>>>> the grid with point sops and finally a transfer attribute that copies
>>>>> color with the 3d information in it to the tracking point. In short this
>>>>> technique worked, but the metaball sampling doesn't seem to be accurate
>>>>> enough and while the point is at the expected position I get random
>>>>> jumps every few frames as it moves. I've tried playing with the kernel
>>>>> values but nothing makes it better.
>>>>> Could any ones suggest a more intelligent (and accurate) approach?
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>>>>>     
>>>>>       
>>>>>         
>>>>>           
>>>>   
>>>>     
>>>>       
>>>>         
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